Commercial scale installation of IAPS as a municipal sewage treatment process is controversial due to the perceived poor performance of the technology (Nemadire 2011, Laxton 2010). Dissection of this perception is regularly hampered by the availability of foreign, efficient and established package plants, such as AS and TF often accompanied by foreign expertise (Nemadire 2011, Rose et al. 2002a). Yet these options may prove inappropriate in the long term, where developing countries lack the necessary infrastructure, expertise and financial resources required to fully exploit these technologies (Nemadire 2011). These conditions are however uniquely suited to the implementation of passive technologies like IAPS. This process takes advantage of naturally occurring warm temperatures, sunlight and gravity and has the potential to generate an algae biomass for fertilizer and methane gas for fuel (Tijjani 2011, Rose et al. 2002a, Green et al. 1996). Thus it becomes imperative to address the concerns surrounding the deployment of IAPS. Findings by Rose
et al. (2007) on the water quality from the ASP suggest a WWT technology unable to
consistently produce an effluent with ≤75 mg.ℓ-1 COD, ≤10 mg.ℓ-1 nitrate-N, ≤6 mg.ℓ-1 ammonia-N, ≤25 mg.ℓ-1 TSS and ≤1 000 cfu.100mℓ-1 faecal coliforms, warranting further investigation to determine the cause of this poor performance. Meiring and Oellerman (1995) previously suggested that the elevated COD and TSS of the treated water from IAPS was a consequence of inadequate design and operation. An elevated COD in the outflow can potentially cause anaerobicity in receiving water bodies (Park and Craggs 2011); yet to circumvent this Green et al. (1995) reported that the water containing algae from the ASPs could be used directly for landscape irrigation and horticulture.
Craggs et al. (2012) later advocated the need for additional treatment of the outflow from ASPs to meet specific environmental discharge standards. Jeong et al. (2015) argue against chlorination to deactivate the algae biomass in this outflow as it causes algae cell rupture
releasing both intra and extracellular polysacharrides. Not only do these polysaccharides contribute to increased dissolved organic C content, they also form chlorinated compounds which may be toxic. Chlorinated nitrogenous disinfection by-products are 140 times more toxic than carbonaceous disinfection by-products (Jeong et al. 2015). Thus it becomes beneficial to minimize the use of chlorination to disinfect this effluent opting rather for UV disinfection (Green et al. 1995). Xu et al. (2014) and Craggs et al. (2012) maintain that the raceway component of an IAPS can be utilized effectively to polish wastewater and to generate a disinfected algae biomass. Algae harvest however remains the problem, though microfiltration is an option (Nemadire 2011, Craggs et al. 2005, Chaumont 1993, de la Noue
et al. 1992). Green et al. (1995) found that a 10-15 d retention in an MP series resulted in
sufficient faecal coliform disinfection for discharge into constructed wetlands (Green et al. 1995). Green et al. (1995) also proposed the use of DAF followed by filtration then UV light disinfection which would result in a water quality from IAPS suitable for unrestricted use.
Pond systems, specifically the traditionally deployed WSPs though passive, require more land than IAPS. Further unlike the IAPS, WSPs do not offer the option to harvest by-products such as methane for heating and cooking or fertilizer for agriculture (Laxton 2010, Rose et al. 2007). Thus far, components of IAPS such as HRAOPs in use in Ashton, Western Cape treat 4 Mℓ.d-1 effluent from fruit canning while the I-PD is used to treat 1.6 Mℓ.d-1 effluent from tomato canning in Musina, Limpopo (Laxton 2010). These installations demonstrate the versatility of the components of IAPS. In addition, several South African-based projects have been initiated for deployment of the IAPS technology to treat municipal sewage, inclusive of a UNEP WioLap sponsored IAPS (1 Mℓ.d-1, Bushman‘s River, Nlambe Municipality), two Partners-for-Water sponsored IAPS (2 Mℓ.d-1 Grahamstown, Makana Municipality; 1.5 Mℓ.d- 1
, Alice, Amathole Municipality), and the conversion of a WSP system to an IAPS (2-3 Mℓ.d- 1
, Bedford, Amathole Municipality). Each project proceeded through the design stage but failed at implementation. Nemadire (2011) attributed the culmination of each to: failure by IAPS to meet South African authorization limits, scarcity of required skills, availability of other technologies (e.g. AS), and delay due to conflicts with stakeholders. Laxton (2010) pointed out a vital factor required for the successful deployment of this type of technology; a multidisciplinary understanding of the technology to comprehensively address socio- economic and environmental prospects to fully benefit from IAPS.
At present many WWTW in South Africa are in disrepair, operate below capacity and intermittently fail while demands on service delivery continue to increase (DWS 2012).
Wastewater treatment can no longer be a linear practice ensuring disease mitigation and eliminating environmental pollution (Rose et al. 2002a, Oswald et al. 1990). Rather employment, energy and product generation need to ensure valorization of WWT practices (Mambo et al. 2014a). In addition, though capital costs should be given their due consideration, long term running and maintenance costs of such facilities are equally if not more important (Nemadire 2011, Laxton 2010). It becomes crucial when a facility malfunctions and foreign expertise is required to resolve technical issues (Nemadire 2011).
Nemadire (2011) states IAPS are 50-70 % more cost competitive to construct, set up and run than AS, TF, and other conventional WWT technologies (Nemadire 2011, Laxton 2010). It is also a simple technology requiring very low skill levels to operate (Rose et al. 2007). The IAPS is a robust technology that is not plagued by electrical issues as with an AS and extended aeration. Construction of IAPS is such that the land can be reclaimed in future for a different purpose, therefore the construction of such a system is not environmentally detrimental (Rose et al. 2002a). Minimal technical equipment such as a pump and electrical batteries for the paddlewheels are required for IAPS functionality (Van Hille et al. 1999). Thus when governments have to bear the capital investment of constructing an IAPS as well as maintenance, costs associated with IAPS are highly competitive (Rose et al. 2002a). Further economically low level jobs are created (Harun 2010). It has also been observed that improved access to clean water simulates social and economic development (Adewumi
et al. 2011, Oswald 1995). The effluent generated by IAPS can be utilized in brick
making, chicken farming, food gardening and as a fertilizer (Rose et al. 2002a, Green et al. 1995). These passive systems are able to withstand varying shock loads while when correctly configured are also capable of consistently generating the desired effluent quality (Muga and Mihelcic 2008, Oswald et al. 1994). As minimal skill levels are required for operation and maintenance of a technology like IAPS, overall it will cost less over an extended period of time to run (Mwabi et al. 2011, Sivakumar et al. 2012, Flores-Alsina et al. 2011). However, despite the vast potential benefits of this technology, the poor performance of the Belmont Valley pilot IAPS needs to be assessed and addressed.